#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,i,a[100][100]={0},j;
	float m=0,max=0;
	cin>>n;
	for(i=0;i<n;i++){
		for(j=0;j<3;j++){
			cin>>a[i][j];
		}
	}
	for(i=0;i<n;i++){
		for(j=0;j<3;j++){
			m=(a[i][0]+a[i][1]) *a[i][2]/2.0;
			if(m>max){
				max=m;
			}
		}
	}
	printf("%.1f",max);
}
/**************************************************************
	Problem: 1330
	User: huxuanchen
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/